A Syrian boy called Doru and his father arrive on British shores in search of a better life. The boy is separated from his old man and ends up homeless in Coventry where rosy-cheeked social worker Miss Shelly places him with a foster mother and enrols Doru at St Bernadette's under headmistress Mrs Keen. Doru arrives just as Mr Johnson and his class are warming up for auditions for a rock opera under formidable director Emmanuel Cavendish.

When you hit rock bottom, the only way is up. That's certainly true of writer-director Debbie Issit's series of improvised comedies, which began in 2009 with the rollicking Nativity!, a feel-good treat steeped in festive cheer. The 2012 sequel subtitled Danger In The Manger! was sporadically entertaining but lacked some of the original's charm. "Wonderful things come in three: musketeers, amigos, times a lady..." notes a madcap teaching assistant in Nativity Rocks!, who evidently didn't have to sit through Nativity 3: Dude, Where's My Donkey?, a pre-Christmas turkey which earned the inglorious distinction of being my worst picture of 2014. Thankfully, the fourth instalment is a small step in the right direction, which shamelessly tugs heartstrings and manipulates our emotions by addressing the global refugee crisis alongside the usual Yuletide tomfoolery...

Marc Wootton has vacated his signature role as deranged teaching assistant Mr Poppy and been replaced by musical theatre star Simon Lipkin as his long-lost brother Jerry. Lipkin's formidable singing talent comes to the fore as the bright-eyed students of St Bernadette's Primary School in Coventry compete for the fictional honour of Christmas Town Of The Year by auditioning for a rock opera.

The film opens on a sombre note with a Syrian boy called Doru (Brian Bartle) and his father (Ramin Karimloo) arriving on these shores in search of a better life. The boy is separated from his old man and ends up homeless in Coventry where rosy-cheeked social worker Miss Shelly (Helen George) places him with a foster mother (Meera Syal) and enrols Doru at St Bernadette's under headmistress Mrs Keen (Celia Imrie). Doru arrives just as Mr Johnson (Daniel Boys) and his class are warming up for auditions under formidable director Emmanuel Cavendish (Craig Revel Horwood), who is an unwelcome face from the past of teaching assistant Jerry Poppy (Lipkin). Jerry takes Doru under his wing and encourages a friendship between the refugee and a wealthy boy called Barnaby (Rupert Turnbull), whose workaholic parents (Anna Chancellor, Hugh Dennis) are too busy to spend the holidays with their lad. Of course, Christmas is a time for miracles and hyperactive man-child Jerry resolves to remind everyone about the importance of family during the festive season with help from a kind-hearted farmer called Beatie (Ruth Jones).

Nativity Rocks! doesn't live up to the promise of its title but there are fleeting moments of amusement drizzled in sugary sentiment. Lipkin fizzes with energy in every frame, even when the film around him is stagnating, while Strictly Come Dancing judge Horwood would be hard pushed to describe his pantomime villain as fab-u-lous. The climactic stage performance to justify Coventry's claim as Christmas Town Of The Year is sweetly shambolic if overlong, reuniting characters with a generous sprinkling of tears.